This invention relates to an alkaline battery and a method of manufacturing an alkaline battery.
Batteries, such as alkaline batteries, are commonly used as energy sources. Generally, alkaline batteries have a cathode, an anode, a separator and an alkaline electrolyte solution. The cathode can include a cathode material (e.g., manganese dioxide or nickel oxyhydroxide), carbon particles that enhance the conductivity of the cathode, and a binder. The anode can be formed of a gel including zinc particles. The separator is disposed between the cathode and the anode. The alkaline electrolyte solution, which is dispersed throughout the battery, can be an aqueous hydroxide solution such as potassium hydroxide.
An alkaline battery includes a cathode including a manganese dioxide having a spinel-type crystal structure (e.g., xcex-MnO2) and an anode including zinc. The alkaline battery can have an average closed circuit voltage of about 1.3V at low rates of discharge, adequate high-rate performance, and sufficient capacity retention when stored. The lambda-manganese dioxide can have a specific discharge capacity at low-rate (e.g., C/30 or 10 mA/g of active cathode material) to a 0.8V cutoff of greater than 310 mAh/g. An average closed circuit voltage of at least about 1.3V can provide voltage compatibility with commercial manganese dioxide-zinc primary alkaline batteries.
In one aspect, an alkaline battery includes a cathode including an active cathode material including lambda-manganese dioxide, an anode including zinc, a separator between the anode and the cathode, and an alkaline electrolyte contacting the anode and the cathode. The active cathode material has a specific discharge capacity to a 0.8V cutoff of greater than 290 mAh/g, greater than 300 mAh/g, greater than 310 mAh/g, or greater than 320 mAh/g, at a discharge rate corresponding to 20 mA/g or 10 mA/g of active cathode material.
In another aspect, a method of manufacturing an alkaline battery includes providing a positive electrode including an active cathode material including lambda-manganese oxide, and forming a battery including the electrode and a negative electrode including zinc particles. Providing the electrode includes preparing lambda-manganese dioxide by contacting water with a compound of the formula Li1+xMn2xe2x88x92O4, wherein x is from xe2x88x920.02 to +0.02 or from xe2x88x920.005 to +0.005, adding an acid to the water and the compound to form a mixture until the mixture has a pH of 1 or less, separating a solid from the water and acid, and drying the solid, optionally in vacuo, at a temperature of 150xc2x0 C. or below to obtain the lambda-manganese dioxide. The alkaline battery has a specific discharge capacity to a 0.8V cutoff of greater than 300 mAh/g at a discharge rate corresponding to 10 mA/g active cathode material.
The lambda-manganese dioxide can have a B.E.T. surface area of between 1 and 10 m2/g (e.g., greater than 8 m2/g), a total pore volume of between 0.05 and 0.15 cubic centimeters per gram (e.g., 0.05 to 0.15 cubic centimeters per gram), or an average pore size of less than 100 A. The acid can be sulfuric acid, nitric acid, perchloric acid, hydrochloric acid, toluene sulfonic acid, or trifluoromethyl sulfonic acid. Concentration of acid can be between 1 and 8 molar. The final pH can be 1 or less, 0.7 or less, or between 0.5 and 0.7. The method can include washing the solid separated from the water and acid with water until the washings have a pH of between 6 and 7.
The solid can be dried at a temperature between 20xc2x0 C. and 120xc2x0 C., between 30xc2x0 C. to 90xc2x0 C., or between 50xc2x0 C. and 70xc2x0 C.
Contacting water and the compound can include forming a slurry. The slurry can be maintained at a temperature between about 5xc2x0 C. and 50xc2x0 C. The temperature of the slurry can be maintained substantially constant during the addition of acid.
Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.